西汉铸钱工艺中钱币型腔和内浇道对充型过程影响的计算机模拟试验

西汉时期平板范竖式浇注铸钱工艺中有不同的钱币型腔设置和内浇道的形状,本研究通过计算机的流动模拟和凝固模拟技术,研究了钱币型腔和内浇道对充型过程的影响。结果表明:1)钱币型腔的不同设置对充型时间影响不大。2)钱币型腔的不同设置对充型过程产生影响,内郭正置的型腔产生气孔等铸造缺陷的可能性增大。3)内浇道的形状对钱币型腔的液流充型时间和液流在型腔中的流动过程有明显的影响,对凝固特征虽略有影响,但远小于钱币本身几何特征对凝固特征的影响。西汉中期起至晚期已基本采用内郭斜置的型腔设置,表明古代工匠在西汉中期始已明了钱币型腔的设置对充型过程将产生影响,已能通过选择更好的钱币型腔的设置来提高钱币的铸造质量。铸钱时,对缩短充型时间的要求高于对充型状态的要求,西汉中期以后多采用缩短充型时间的内浇道形状以提高平板范竖式浇铸工艺的充满率,从而提高成品率。

Simulation studies on the influence of ingate and mold cavities on Western Han Dynasty bunchcasting processes for making bronze coins

From the early to the late Western Han dynasty (206B.C. 9A.D.), the ingate shape and mold cavity arrangement used in the bunchcasting of bronze coins underwent change. In this paper, computer simulated casting processes were used to study the effect of ingate shape and mold cavity on mold filling and solidification. The results showed the following:1) The mold cavity arrangement has little impact on the mold filling time. 2) The design inside the mold has an effect on the molding process:when the inner mold is straight in the middle, it is likely to cause air bubble and other defects. 3) The ingate shape influences both the mold filling process and mold filling time, but has little effect on the solidification process, with regard to the coin's shape. From the middle to the late Western Han Dynasty, an oblique inner mold was commonly used, suggesting that the Han Dynasty technician already understood the effect of the inner mold on the molding process, and therefore could selectively choose a better inner mold design. During the coin molding process, a shortened filling time is desired, preliminary to the molding process. Since the middle of the Western Han Dynasty, an inner mold that had a shorter filling time was commonly used to increase the filling capability, and meanwhile, increased qualification yield.